A lot of people (myself included), don’t have home racks to make money. That never even enters the equation.
I have a home rack for training (I work in IT), for mass storage (films and TV shows, software – keeping it internal to my home network means I don’t rely on the internet being online), and for failover networking (working from home and home “smart” devices mean constant uptime is a necessity).
And as somebody else said, old hardware is cheap (comparatively).
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